Fluidic motion-limiting system for motor-driven apparatus

ABSTRACT

An operator&#39;&#39;s control lever which is shifted to actuate a hydraulic motor is returned to the initial position to stop the motor after a preselected amount of travel of a element driven by the motor. A fluidic circuit has means producing digital signals indicative of successive increments of travel of the element and has a counter for storing any preselected number of such signals. When the selected count is reached, a kickout means manipulates the operator&#39;&#39;s control lever to stop further operation of the motor. The count required to stop the motor, and thus the amount of travel of the element, may be changed by turning of a control knob. The system is applicable, for example, to limiting movement of the lift arms of a loader vehicle.

United States Patent 13,613,505

[72] Inventor Th m J. Bubula 1 3,305,170 2/1967 Zilberfarb 235/201 J 3,318,523 5/1967 Bauer et al 235/201 I 5 1 2 6 Primary Examiner-Martin P. Schwadron g 1971 Assistant Examiner-C. Schimikowski [73] Assignee catrpinar Tractor C 0. Attorney-Fryer, Tjensvold, Feix, Phillips & Lempio Peoria, Ill.

[54] FLUIDIC MOTION-LIMITING SYSTEM FOR MOTOR DRIVEN APPARATUS ABSTRACT: An operators control lever which is shifted to 10 Claims 4 Drawing Figs actuate a hydraulic motor is returned to the initial position to stop the motor after a preselected amount of travel of a ele- [52] US. Cl 91/35,

ment driven by the motor. A fluidic circuit has means produc- 235/201, l37/624J8, 1 7/ i digital signals indicative of successive increments of travel [51] Int. Cl ..Fl5b 21/02, f the element and has a counter f storing any preselected 606d 1/04, Flsc llog number of such signals. When the selected count is reached, a

[50] Field of Search r. 91/], 35,

kickout means mani ulates the o erators control lever to P P 235/201 stop further operation of the motor. The count required to [56], Reerences Cited stop the motor, and thus the amount of travel of the element,

may be changed by turning of a control knob..T hc system is UNITED STATES PATENTS applicable, for example; to limiting movement of .the lift a'rms 3,241,668 3/1'96'6 Schonfeldeta'lnl 235/201 'ofa-loadervehicle.

PATENTEDUCI 19 197i 3,613,505

SHEET 10F 3 INVENTOR THOMAS J. BUBULA ATTORNEYS PATENTEnu m 19 ISII SHEEI 2 BF 3 RNSE' LOWER INVENTOR THOMAS J. BUBULA PATENTEDHCT 1 Ian 3,613,505

SHEET 3 BF 3 n II5 & 7 I07 og A04 03 iOG 83 5 INVENTORS THOMAS J. BUBULA W1 W4 any 11 ,4 3m

FLUIDIC MOTION-LIMITING SYSTEM FOR MOTOR- DRIVEN APPARATUS BACKGROUND OF THE INVENTION This invention relates to systems for limiting the amount of movement of motor-driven apparatus and more particularly to a system for stopping the movement of a motor-driven element at a preselected point in the travel of the element.

Many fonns of motor-operated apparatus are equipped with motion-limiting means which automatically stops the motor after a predetermined amount of travel of a driven element. In certain equipment of this kind, itis necessary that the operator be able to adjust the system to change the amount of permitted travel of the element. In the absence of cumbersome linkage or complex electrical components, prior motion-limiting means of this kind have not been readily adjustable-in this manner. In'most cases, the operator must shut down the apparatus and leave his normal station-and make the-necessary adjustments in the area of the moving element. Many such prior systems require that motion-sensing means be situated at a location where the possibility of damage is high. Still further, such prior systems tend to be undesirably bulky, costly, prone to jamming and are not readily adaptable to different forms of powered mechanism.

The kickouts or positioners used to stop raising and lowering of the bucket on a loader vehicle are typical of the motionlimiting mechanisms discussed above and the invention will be herein described with reference to a loader, it being apparent that the invention is also applicable to other powered apparatus. V

The bucket of a loader is carried by lift arms which are pivoted to a tractor vehicle and one or more hydraulic jacks, responsive to shifting of an operators lever, provide for raising and lowering'iof the arms and the bucket. Detents are usually provided to hold the control lever in either of the raise or lower settings so that the operator need only initially position the control lever and may then remove his hand from the lever and turn his attention to other tasks while the bucket rises or drops. Kickouts of the kind referred to above are mechanisms which sense when the bucket has been lowered to raised to a predetermined desired position and then automatically release the detents so that the control lever returns to the hold position to stop further bucket movement without requiring any action on the part of the operator.

As heretofore constructed, such kickout systems are subject to the disadvantages of motion-limitingmeans in general as discussed above. Notably, any adjustment of the point of bucket travel at which the kickouts operate is difficult in that the operator must stop the loader,-dismount from his station,

and make time-consuming and intricate manipulations. When- SUMMARY OF THE INVENTION This invention is a compact, inexpensive and highly reliable motion-limiting system for motor-driven apparatus which may be readily adjusted to change the limit of motion of an element with such adjustment being made by simply changing the setting of an adjustable control which may be located by'any convenient point.

The invention provides means for sensing movement of the motor-driven element to produce digital signals in a fluidic logic circuit wherein the accumulated total of such signals is indicative of the distance traveled by the moving element. After a predetermined number of such signals have been generated and counted, the motor control is automatically operated to stop the motor to limit further travel of the moving element. The number of counts needed to effect such action is variable as desired by changing the setting of a control which may be located at a position convenient to the operator.

Accordingly, it is an object of this invention to provide a motion-limiting system for motor-driven apparatus which may be readily adjusted to effect changes in the limit of motion of a moving element.

It is a further object of the invention to provide a compact, sensitive and versatile motion-limiting system for powered mechanisms which system has few moving parts and does not required the disposition of fragile elements at points where the potential for damage is high.

It is still another object of the invention to provide a more convenient and reliable kickout system for use in conjunction with the operator's controls of load manipulating elements in loader vehicles and the like.

The invention, together with further objects and advantages thereof, will best be understood by reference to the following description of a preferred embodiment in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a side elevation view of a front-end loader, with portions thereof broken out, in which the present invention is utilized for automatic stopping of the raising and lowering of the loader bucket,

FIG. 2 is a side elevation view of the operators control lever of the loader of FIG. 1 with certain hydraulic elements, operated by the lever, being shown in schematic form,

FIG. 3 is a section view of the operator's control mechanism of FIG. 2 taken along staggered line IIIIII thereof; and

FIG. 4 is a fluidic circuit diagram showing elements of the lift arm motion-limiting system of the loader of FIGS. 1 to 3.

Referring initially to FIG.-] of the drawing, salient elements of a loader 11 include a tractor [2 having a bucket 13 pivoted to the front end of forwardly directed lift arms 14. To provide for vertical travel of the bucket 13, the rearward end of the lift arms are coupled to the tractor body by pivot connections 17 and fluid motors 16, generally a pair of hydraulic jacks, are coupled between the lift arms and the tractor body. Tilt linkage 18 is coupled between the bucket I3 and tractor body to maintain the bucket at a substantially constant inclination as the lift arms 14 are raised or lowered, with the linkage being formed in part of additional hydraulic jacks 19 which provide for pivoting of the bucket relative to the lift arms to perform rack back, dumping and other operations.

The lift motor 16 is controlled by manipulating a control lover 21, situated at the operator's station 22, which connects with a spool valve 23 through linkage 24. As shown schematicallyin FIG. 2, spool valve 23 may be a three-position valve with a RAISE setting at which a pump 26 delivers fluid from a supply reservoir 27 to the head end of lift motor I6 while venting the rod end of the motor to the reservoir. Valve 23 has a LOWER setting at which the output of the pump is transmitted to the rod end of lift motor 16 while the head end is vented and further has an intermediate HOLD setting at which the ports at both ends of the motor are closed while the output of pump 26 is diverted directly back to the reservoir 27. Control lever 21 is pivoted at its base to a support housing 28 for movement between the RAISE, HOLD, and LOWER settings and acts to shift the valve 23 between the above-described positions thereof through linkage 24.

Referring now to FIG. 3 in conjunction with FIG. 2, the' lower end of control lever 21 extends into a slot 29 in support housing 28 and is transpierced by a pivot shaft 31 to provide for the fore and aft movement of the lever. To provide a hydraulically actuated detent mechanism 32 for temporarily holding lever 21 at a selected position, shaft 31 is formed as an axial projection on a piston 33 which is slidable within a'circular chamber 34 in the support housing 28 in a direction normal to the plane of movement of lever 21 whereby the piston may be moved to clamp the lever in a selected position. To actuate the piston 33 for this purpose, the outer side of chamber 34 is defined by a circular closure 36 having a port 37 into which high-pressure fluid may be admitted and released. Shaft 31 extends through the base of lever 21 into a bore 38 in the opposite side of the support housing 28 and a compression spring 39, held by a fixed retainer pin 41, acts against the end of the shaft to urge piston 33 away from lever 21 so that the lever is not clamped in a fixed position except when fluid pressure in the chamber 34 overcomes the force of spring.

To urge lever 21 toward the center or HOLD setting, a table 42 extends downwardly from the lower end of the lever between spaced-apart downwardly directed legs 43 of the support housing 28 and one of a pair of compression springs 44 is disclosed between the tab and each leg 43.

The structure of FIGS. 1 to 3 as described to this point provides a means for manually controlling the raising and lowering of the loader lift arms 14 and bucket 13 by manipulating control lever 21. However, the above described mechanism by itself would require that the operator hold lever 21 in either the RAISE or LOWER settings for the full time period required to raise or lower bucket 13 the desired amount. To avoid this requirement, the invention provides fluidic circuitry whichactuates the detent mechanism 32 to hold the control lever 21 at each of the RAISE and LOWER positions of the lever until the lift arms and bucket have risen or lowered to predetermined levels at which point the detent mechanism is automatically released enabling springs 44 to return the control lever to the- HOLD position and stop further movement of the lift arms. 7

Referring now to FIG. 4 in conjunction with FIG. 3, the detent mechanism 32 is operated and released by shifting of a two-position spool valve 46. Valve 46 has a spool 47 which may be shifted, by application of air under pressure to a first control port48, to couple the hydraulic fluid pump 26 to a conduit 37' connected to the previously described detent mechanism port 37 thereby actuating the detent to hold the control lever 21 at a selected setting. Application of air under pressure to an opposite port 49 of spool valve 46.shifts spool 47 connect conduit 37 with the drain reservoir 27 thereby releasing the detent mechanism 32 whereby the control lever 21 is spring returned to the HOLD setting.

Fluidic circuit elements which control the spool valve 46 are shown in FIG. 4 wherein standard symbols for fluidic logic are sued withthe letter S designating connections to a source of air under pressure and the letter E designating Exhaust or Vent ports of the several fluidic components. While the circuit will be described as utilizing pneumatic components, it will be apparent that the same circuit is adaptable to hydraulic fluidic elements.

In order to actuate the detent mechanism, movement of the control lever 21 into the LOWER or RAISE setting is detected by fluidic Schmitt triggers 51 and 52 respectively. Schmitt trigger 51 has control channels53 and 53' connected to the air supply S through resistors (flow constructions) 54 and 54' with control channel 53 also being connected to a conduit 56 to the control lever assembly. Referring now again to FIGS 2 and 3 in conjunction, conduit 56 connects with a passage 57 in lever support housing 28, the passage having an end 58 situated to be blocked by lever 21 in the HOLD and RAISE settings thereof but which is uncovered, to vent the pressure in conduit 56 when the lever is shifted to the LOWER setting.

Referring again to FIG. 4, this release of pressure from conduit 56 and control channel '53 enables the air flowing into the opposite control channel 53 to shift the flow of air through Schmitt trigger 51 from vent channel E to output channel 62. Output channel 62 then transmits air to one input 63 of an OR-gate 64 which responds by transmitting air through output channel 66 to one input 67 of an OR-gate 68 causing pressure to be switched form a first output channel 69:0f OR-gate 68 to the second output channel 60' thereof. Output channel 69 connects with port 49 of spool valve'46 while output channel 69' connects with port 48 thereof. Thus, the above-described action of OR-gate 68 causes spool 47 to shift to couple pump 26 with conduit 37 thereby actuating the detent mechanism 32 of FIG. 3 to clamp the lever 21 at the LOWER setting. Thus, anytime that the operator shifts the lever 21 into the LOWER setting, it is immediately held thereat by the actuation of the detent mechanism 32 as described above.

A similar action occurs if the lever 21 is shifted in the other direction to the RAISE setting. Referring again to FIGS. 2 and 3, a second passage 71 in support housing 28 has an end 72 situated to be blocked by lever 21 when the lever is in the HOLD or LOWER settings but which is uncovered when the lever is moved into the RAISE setting, thereby venting a conduit 73. Referring now again to FIG. 4, conduit 73 connects with the signal input channel 74 of Schmitt trigger 52, the input channel 74 and the opposite control channel 74' being connnected to air supply S through resistors 76. As in the previous instance, the release of pressure from conduit 73 enables the airflow into control channel 74' to switch the flow through the Schmitt trigger from the vent channel E to output channel 78. Channel 78 connects with the other input 63' of OR-gate 64. Consequently, through the previously described action of OR gates 64 and 68, the movement of the control lever into the RAISE setting also operates spool valve 46 to actuate the detent mechanism 32, thereby holding the control lever at the RAISE setting.

Thus, the control lever is immediately held at either the RAISE or LOWER positions once it is moved to such positions and the operator may remove his hand and direct his attention to controlling other aspects of the vehicle during the period that the lift arms rise or fall. This desirable mode of operation further requires that means he provided for determining when the lift anns have risen or lowered the desired amount and further requires means which then releases the detent automatically so that the control lever springs back to the HOLD position and stops further lift arm movement. Referring to FIGS. 1 and 4 in combination, a position digitizer cylinder'79 is connected between the body of tractor l2 and lift arms 14, by pivot connections 81, to generate fluidic digital signals indicative of movement of the lift arms.

Referring again to FIG. 4 in particular, digitizer cylinder 79 includes a cylinder 82 and a rod 83 which is slidable therein in an axial direction whereby lowering of the lift arms contracts the rod into the cylinder and raising of the lift arms extends the rod further out of the cylinder. A passage 84 within the rod 83 is coupled to air supply S through a resistor 86 and connects with a port 87 in the side of the rod. Port 87 is normally blocked by the adjacent inner wall of cylinder 82 but passes across a port 88 in the side of the cylinder, as the lift arms approach the lower portion of the downward travel.

Momentary venting of rod port 87 in this manner generates a fluidic signal which conditions a binary counter 89, comprised of a series of fluidic binary counting elements 91, to begin a count indicative of the amount of further downward travel of the lift arms. In particular, the signal input control channel 92 of another fluidic Schmitt trigger 93 is connected to rod passage 84 with the other control channel 92 being connected to air supply S through a resistor 94 whereby the passage of port 87 past port 88 diverts the flow of air in the Schmitt trigger 93 from vent channel E to an output channel 96. Channel 96 connects to one control channel 97 of a fluidic flip-flop 98 and the signal applied thereto switches the airflow through the flip-flop from an outlet channel 101, which connects with the reset channel 102 of each of the binary counting elements 91, to a vent channel E of the flip-flop. This action depressuriies reset lines 102 of the binary counting elements 91 to condition the counter 89 to begin a counting sequence.

Signals indicative of further movement of the rod 83 into cylinder 82 are generated by momentary exhausting of a passage 103 rod 83 as an end port 104 thereof passes along a series of ports 106 in the wall of cylinder 82. Passage 103 is connected with the air supply S through a resistor 107 and also connects with the signal input channel 108 of another Schmitt trigger 109. The other control channel 108' of Schmitt trigger 109 connected to the air supply through a resistor 111 and thus passage of port 104 past each of the cylinder ports 106 acts to momentarily divert the airflow through Schmitt trigger 109 from vent E to an output channel 112. Output channel 112 is connected with the signal input A of the first of the series of binary counting devices 91.

Binary counter 89 is comprised of four of the counting devices 91, here identified as 91a, 91b, 91c, and 91d, each having an input A and outputs F1 and F2 in addition to the common reset input 102. The input A of each device 91, other then the first, is coupled to the F2 output of the preceding device so that the sequence operates as abinary counter in a manner understood in the data processing art. In particular, the first device 91a changes state with each incoming signal while the second device 91b changes state with every other incoming signal and the ice 91c changes state with every fourth signal while the final device 91d changes state only upon the eighth signal of the sequence. Thus, the devices 91 'pintly assume a condition after each incoming signal which is unique and indicative of the number of such signals that has been received at that time.

To monitor the count stored in counter 89, to initiate stopping of the downward movement of the loader lift arms at a preselected time, a sequence of four AND-gates 118a to 118d are connected between the counting devices 91 and a sequence of eight distinct fluid signal channels 122-1 to 122-8. AND-gates 118 function to pressurize the particular one of the channels 122 which corresponds to the number of counts which has been received by counter 89 at any given time. For this purpose, the F1 output of device 91a is coupled to one input A of AND-gate 118a and is also coupled directly to channel l22l.-Thus, channel 122-l is energized when the first count is received by counter 89 inasmuch as device 91a changes state at that time to pressurize its output F 1. Output F l of device 91b is connected with channel 1222 and also to one input A of AND-gate 1l8b. Thus, channel l222 is pressurized after the second incoming signal as 91b changes state at this time to pressurizeits output F 1. Output P1 of device 91b is also coupled to the other input B of AND-gate 1180 while the output F of gate 118a is coupled to the third channel 122 -3. Thus, the above described connections provide for pressurization of channel 122-3 after the third signal is received, inasmuch as bothinputs A and B of AND-gate 118a are pressurized at that time and therefore the AND gate transmits pressure to its output F and thus to line l223. The output F 1 of device 910 is coupled directly to channel 122-4 ad device 91c first changes state upon the fourth signal. Channel 122-5 is pressurized upon the fifth signal in that it is coupled to the output F of AND-gate 118b which has one input A coupled to output F1 of device 91d and the other input B coupled to output F of AND-gate 118a so that the condition existing after the fifth pulse enables gate 11% to transmit pressure to its output F1. To pressurize channel 122-6 after the sixth pulse, the output F of AND-gate "Se is coupled to channel 122-6 with the inputs of gate 118a being coupled respectively to the output of AND-gate 11812 and the F1 output of device 91a. Channel 122-7 is pressurized after the seventh incoming signal through a connection to the output F of AND-gate 118d, the two inputs of gate 118d being connected respectively to the output F of AND-gate 118a and the output Fl of counting device 910. Channel 122-8 is pressurized after the eighth pulse through a direct connection to output F1 of the final counting device 912 which does not change state until the last signal of the sequence y is received.

Considering'now an important aspect of the invention, the operator is provided with a manually adjustable multiposition fluidic switch 119 for selecting the point at which motion of the lift arm and buckets is to be automatically stopped. As

shown in FIG. 1, the switch 119 may include a rotatable knob 119' positioned within easy reach of the operator's hand at operator's station 22, the switch being located on the console at the front of the operators station in this instance. Referring now again to FIG. 4, switch 119 has a series of settings including an off or zero position and a number of additional positions equal to the number of channels 122, there being eight such additional positions in thisexample. Rotation of knob 119' to any of the positions thereof connects an output line 121 with a corresponding one of the channels 122. Thus, output line 121 will be pressurized when the particular channel 122 associated with the selected setting of dial 119 is pressurized as described above. Thus, the point in the travel of rod 83 into cylinder 82 at which switch output line 121 is pressurized is determined by the selected setting of switch 119 and may be varied as desired by adjusting the knob 119'.

Pressurizing of the switch output line 121 in this manner transmits air to one input channel of an AND-gate 124 which has the other input channel already pressurized through a connection 126 to the previously described output channel 62 of Schmitt trigger 51 which was pressurized by the original manipulation of the control lever. Accordingly, the airflow through AND-gate 124 is switched to the output channel 127 of the gate. Output terminal 127 is coupled to the second control channel 67' of the previously described OR-gate 68 that controls spool valve 46. Receipt of a signal at the second control channel 67' of gate 68 returns the airflow therethrough from port 48 of spool valve 46 back to port 49 thereof thereby shifting spool 47 to vent conduit 37 Referring now again to FIGS. 2 and 3 in conjunction, venting of conduit 37 releases the detent mechanism 32 enabling springs 44 to return the control lever 21 to the center or HOLD position. This shifts the lift motor control valve 23 to stop further travel of the lift arms.

Referring now again to FIG. 4, the circuit operates in an essentially similar manner to stop raising of the lift arms at any preselected one of a number of points. As rising of the lift arms extends rod 83 from cylinder 82, an additional port 88 in the cylinder is positioned to momentarily vent port 87 as the lift arms approach the final portion of upward travel. As previously described, the momentary exhausting of rod passage 84, acting through Schmitt trigger 93 and flip-flop 98 conditions the binary counter 89 for a counting sequence. As the rod 83 extends further, fluidic signals are generated periodically by momentary venting of rod passage 103 by an additional series of ports 106 which are similar to ports 106 but situated near the opposite end of cylinder 82.

Such signals are counted as previously described with respect to lowering of the lift arms. The number of counts required to stop raising of the lift arms is determined by the setting of a second multiposition fluidic switch 128 which is also situated at 128 5 station 22 of the loader as shown in HO. 1. Referring again to FIG. 4, setting of a knob 128 of switch 128 at any of the positions thereof other than the initial or OFF position connects an output line 121' with one of the previously described channels 122 each of which is pressurized after a corresponding number of signals have been received at counter 89. Pressurizing of output line 121 because of the accumulation of the requisite number of counts applies air pressure to one of the control channels of an AND- gate 124'. The other control channel of gate 124' is coupled to output channel 78 of Schmitt trigger 52. AND-gate 124' then transmits air pressure through output channel 129 to control channel 67' of OR-gate 68. Gate 68 responds by shifting spool valve 46 to deenergize the detent mechanism 32 of FIGS. 3 and 4 thereby releasing the control lever 21 and stopping further extension of lift motor 16.

Referring now again to FIG. 1, while the motion-limiting system has been herein described with reference to the action of the lift motors 16 in raising and lowering the lift anns 14 and buckets 13, it will be apparent that such a system may also be utilized to automatically limit the action of tilt motors 19 in pivoting the bucket 13 about the end of the lift arms.

crawler tractor loaders of the kind herein described for purposes of example, but hasdiverse usages'where, motor-driven elements are to be automatically stopped at a predetermined and adjustable point in the travel thereof.

What is claimed is:

. 1. A system for stopping movement of a motor-driven element at any selected one of a plurality of points in the travel of said element comprising a motor a motor control having a first position at which said motor is actuated and a second position at which said motor is stopped,

a fluidic signal generator coupled to said element and responding to movement of said element by producing a fluidic signal as said element reaches each of a plurality of points in said travel thereof,

fluidic signal-counting means coupled to said signal generator for counting the number of said signals produced thereby, and I fluid circuit means coupled between said signal-counting means and said motor control for shifting said motor control to said second position thereof after receipt of a predetermined number of said fluidic signals at said counting means, said fluid circuit means having an adjustable component for selecting the number of said signals required to shift said motor control to said second position thereof.

2. The combination defined in claim 1 wherein said motor control is manually operable and further comprising means urging said control toward said first position thereof and further comprising a fluidoperated detent holding said control at said second position thereof after being manually moved to said second position, said fluid circuit means being coupled to said detent to release said detent after receipt of said preselected number of fluidic signals at said counting means.

3. The combination defined in claim 2 wherein said motor control is a lever and said detent has a fluid pressure-controlled member movable against said lever to clamp said lever at said first position thereof and wherein a valve is coupled between said member and a source of fluid under pressure to operate said detent and wherein said fluid circuit means is comprised of an element defining a fluid passage with a port which is vented and closed by movement of said lever between said positions thereof to generate a fluidic signal upon movement of said lever to said first position thereof, and fluidic circuit means coupled between said passage and said valve for operating said valve to apply said detent to said lever in response to said signal in said passage.

4. The combination defined in claim 2 further comprising a source of fluid under pressure, a detent control valve coupled between said fluid-operated detent and said source and having one position transmitting fluid from said source to said detent and having another position exhausting said detent, said detent control valve being shifted between said positions thereof in response to fluidic signals, means shifting said detent control valve in response to movement of said motor control to said first position thereof whereby said detent is actuated to hold said motor control lever thereat, and means generating a fluidic signal to shift said detent control valve back to the other position thereof after receipt of said preselected number of fluidic signals at said counting means whereby said detent is released- 5. The combinations defined in claim 1 wherein said fluidic counting means is comprised of a series of fluidic binary counting devices each having a signal input and a pair of outputs with the input of a first device being coupled to said signal generator whereby said devices jointly assume a condition after each incoming signal which is indicative of the total number of signals received at that time, said control circuit means being comprised of a plurality of fluid channels, logic circuit means coupled between said binary-counting devices and said channels for transmitting a signal to the one of said channels corresponding to the number of counts registered by said counting means, a manually adjustable multiposition valve having a plurality of inputs each connected to a separate one of said channels and having an output signal channel selectively connectable with any one of said inputs, and means for shifting said motor control to said second position thereof in response to a signal in said output channel of said multiposition valve.

6. The combination defined in claim I wherein said fluidic signal generator is comprised of a cylinder having a plurality of openings spaced-apart along the length of the wall thereof, a rod extending within said cylinder in coaxial relationship therewith and being slidable in an axial direction relative thereto, said rod having a first passage with a port which passes successive ones of said openings of said cylinder as the rod is moved axially relative thereto, coupling means providing for relative movement between said rod and said cylinder in response to movement of said motor-driven element, a source of fluid under pressure coupled to said passage of said rod, and a flow restriction connected between said source of fluid and said passage of said rod whereby the pressure within said passage is momentarily reduced to produce a fluidic digital signal as said port passes each of said openings of said cylinder.

7. The combination defined in claim 6 further comprising a fluidic Schmitt trigger having a signal input control channel coupled to said passage of said rod and having a second control channel coupled to said air supply through a flow construction and having an output channel coupled to said fluidic signal counting means whereby venting of said passage of said rod as said port thereof passes each of said openings of said cylinder actuates said Schmitt trigger to deliver a signal to said fluidic signal counting means.

8. The combination defined in claim 6 wherein said rod has an additional passage and port, said additional port being situated to be vented by an opening in the wall of said cylinder during movement of said rod relative to said cylinder prior to the juxtaposition of said port of said first passage with the first of said openings, said additional passage of said rod being coupled to said air supply through a second flow constriction whereby the pressure in said additional passage is momentarily reduced as said additional port is vented to produce a start of count signal in said second passage, and means transmitting said start of count signal to the reset line of said fluidic signal counting means.

9. The combination defined in claim 6 wherein said system stops movement of said motor-driven element in each of two directions of travel thereof, said cylinder having a first portion of said plurality of openings near one end section of the cylinder and having the other portion of said plurality of openings near the opposite end section of the cylinder whereby a sequence of fluidic digital signals is generated in said rod passage as said rod approaches maximum contraction into said cylinder and as said rod approaches maximum extension from said cylinder.

10. The combination defined in claim 9 wherein the fluid circuit means coupled between said signal-counting means and said motor control has a pair of said adjustable components for selecting the number of said signals required to shift said motor control to said second position thereof whereby the position at which said motor-driven element is stopped at one extreme of travel thereof may be changed independently of the position at which said element is stopped at the other extreme of travel thereof. 

1. A system for stopping movement of a motor-driven element at any selected one of a plurality of points in the travel of said element comprising a motor a motor control having a first position at which said motor is actuated and a second position at which said motor is stopped, a fluidic signal generator coupled to said element and responding to movement of said eLement by producing a fluidic signal as said element reaches each of a plurality of points in said travel thereof, fluidic signal-counting means coupled to said signal generator for counting the number of said signals produced thereby, and fluid circuit means coupled between said signal-counting means and said motor control for shifting said motor control to said second position thereof after receipt of a predetermined number of said fluidic signals at said counting means, said fluid circuit means having an adjustable component for selecting the number of said signals required to shift said motor control to said second position thereof.
 2. The combination defined in claim 1 wherein said motor control is manually operable and further comprising means urging said control toward said first position thereof and further comprising a fluid-operated detent holding said control at said second position thereof after being manually moved to said second position, said fluid circuit means being coupled to said detent to release said detent after receipt of said preselected number of fluidic signals at said counting means.
 3. The combination defined in claim 2 wherein said motor control is a lever and said detent has a fluid pressure-controlled member movable against said lever to clamp said lever at said first position thereof and wherein a valve is coupled between said member and a source of fluid under pressure to operate said detent and wherein said fluid circuit means is comprised of an element defining a fluid passage with a port which is vented and closed by movement of said lever between said positions thereof to generate a fluidic signal upon movement of said lever to said first position thereof, and fluidic circuit means coupled between said passage and said valve for operating said valve to apply said detent to said lever in response to said signal in said passage.
 4. The combination defined in claim 2 further comprising a source of fluid under pressure, a detent control valve coupled between said fluid-operated detent and said source and having one position transmitting fluid from said source to said detent and having another position exhausting said detent, said detent control valve being shifted between said positions thereof in response to fluidic signals, means shifting said detent control valve in response to movement of said motor control to said first position thereof whereby said detent is actuated to hold said motor control lever thereat, and means generating a fluidic signal to shift said detent control valve back to the other position thereof after receipt of said preselected number of fluidic signals at said counting means whereby said detent is released.
 5. The combinations defined in claim 1 wherein said fluidic counting means is comprised of a series of fluidic binary counting devices each having a signal input and a pair of outputs with the input of a first device being coupled to said signal generator whereby said devices jointly assume a condition after each incoming signal which is indicative of the total number of signals received at that time, said control circuit means being comprised of a plurality of fluid channels, logic circuit means coupled between said binary-counting devices and said channels for transmitting a signal to the one of said channels corresponding to the number of counts registered by said counting means, a manually adjustable multiposition valve having a plurality of inputs each connected to a separate one of said channels and having an output signal channel selectively connectable with any one of said inputs, and means for shifting said motor control to said second position thereof in response to a signal in said output channel of said multiposition valve.
 6. The combination defined in claim 1 wherein said fluidic signal generator is comprised of a cylinder having a plurality of openings spaced-apart along the length of the wall thereof, a rod extending within said cylinder in coaxial relationship therewith aNd being slidable in an axial direction relative thereto, said rod having a first passage with a port which passes successive ones of said openings of said cylinder as the rod is moved axially relative thereto, coupling means providing for relative movement between said rod and said cylinder in response to movement of said motor-driven element, a source of fluid under pressure coupled to said passage of said rod, and a flow restriction connected between said source of fluid and said passage of said rod whereby the pressure within said passage is momentarily reduced to produce a fluidic digital signal as said port passes each of said openings of said cylinder.
 7. The combination defined in claim 6 further comprising a fluidic Schmitt trigger having a signal input control channel coupled to said passage of said rod and having a second control channel coupled to said air supply through a flow construction and having an output channel coupled to said fluidic signal counting means whereby venting of said passage of said rod as said port thereof passes each of said openings of said cylinder actuates said Schmitt trigger to deliver a signal to said fluidic signal counting means.
 8. The combination defined in claim 6 wherein said rod has an additional passage and port, said additional port being situated to be vented by an opening in the wall of said cylinder during movement of said rod relative to said cylinder prior to the juxtaposition of said port of said first passage with the first of said openings, said additional passage of said rod being coupled to said air supply through a second flow constriction whereby the pressure in said additional passage is momentarily reduced as said additional port is vented to produce a start of count signal in said second passage, and means transmitting said start of count signal to the reset line of said fluidic signal counting means.
 9. The combination defined in claim 6 wherein said system stops movement of said motor-driven element in each of two directions of travel thereof, said cylinder having a first portion of said plurality of openings near one end section of the cylinder and having the other portion of said plurality of openings near the opposite end section of the cylinder whereby a sequence of fluidic digital signals is generated in said rod passage as said rod approaches maximum contraction into said cylinder and as said rod approaches maximum extension from said cylinder.
 10. The combination defined in claim 9 wherein the fluid circuit means coupled between said signal-counting means and said motor control has a pair of said adjustable components for selecting the number of said signals required to shift said motor control to said second position thereof whereby the position at which said motor-driven element is stopped at one extreme of travel thereof may be changed independently of the position at which said element is stopped at the other extreme of travel thereof. 